The present invention relates to wireless telemetry systems in general and, more particularly, for medical purposes.
Wireless telemetry is generally defined as a (more or less automated) communication process by which measurements are made and/or other data collected at remote or inaccessible points, and transmitted (using wireless radio transmission) to a receiving equipment for monitoring, display, and/or recording. In particular medical applications increasingly apply wireless telemetry systems, e.g. for pulse oximetry or electrocardiography. The term telemetry as used hereinafter shall apply to wireless telemetry systems only.
Telemetry systems normally comprise a transmitter for transmitting electromagnetic signals, e.g. from a measurement, and a receiver for receiving the electromagnetic signals from the transmitter. In current medical telemetry systems, the transmitter is usually carried by the patient and the receiver is typically installed in an operator room. Large systems may have a multitude of transmitters and receivers. Each transmitter normally operates with a corresponding receiver on a certain channel, preferably over a pre-defined carrier frequency.
In medical applications, in particular, it is often required to simultaneously monitor a plurality of different parameters, such as heart rate or oxygen saturation, each requiring a specific measuring setup. Telemetry systems, on the other hand, are intentionally applied, in some applications, in order to improve a patient""s comfort, freedom and privacy or to be used for monitoring during transportation. Thus, it is desired to reduce the number and volume of devices directly or indirectly attached to the patient.
The most common telemetry systems in medical applications are single-parameter telemetry systems, whereby a complete telemetry system comprising sensor and transmitter is required for each parameter to be monitored. Consequently, hospitals need a plurality of different transmitters for each parameter, thus requiring a high demand of logistics, and, more seriously, a different transmitter has to be applied to the patient for changing monitoring from one parameter to another.
The Agilent Viridia 50 T (M1310A) Fetal Telemetry System of Agilent Technologies addresses the contravening objectives of, on one hand, monitoring a plurality of parameters and, on the other hand, reducing the number of required telemetry components. The system allows monitoring the parameter fetal heart rate (FHR) via ultrasound or direct electrocardiogram (ECG), and the parameter uterine activity via an external Toco transducer or an internal intrauterine pressure (IUP) transducer. As depicted in FIG. 1, up to two transducers 10 and 20 can be connected to a small lightweight transmitter 30 that is worn by the patient. Signals representing the parameters fetal heart rate, uterine activity and fetal movement profile (FMP) are transmitted continuously via radio frequency from the transmitter 30 to a (not shown) telemetry receiver, where the signals are displayed and recorded on a monitor.
Another constraint in medical applications is that the spacing (typically 25 kHz) and bandwidth of radio frequency (RF) channels in bands is usually fixed due to telecommunication regulations. While the limited bandwidth limits the amount of data that can be transmitted, even a low bandwidth parameter has to use a full bandwidth RF channel thus wasting limited RF spectrum.
The aforementioned Agilent Viridia 50 T Fetal Telemetry System allows to simultaneously transmit the (higher bandwidth) parameter of fetal heart rate (FHR) and the (lower bandwidth) parameter of uterine activity within one RF channel and via one RF transmitter. This addresses both, the limited RF bandwidth problem and also logistics problems since the number of components and different transmitters is reduced.
Another solution to overcome the limited RF bandwidth, as applied e.g. in the Agilent M2601A series also of Agilent Technologies, is to add selection means to an ECG transmitter for selecting one ECG wave out of many leads connected to the patient, and transmitting only the selected wave. A further solution, also applied e.g. in the Agilent M2601A series, is to transmit two ECG waves (higher bandwidth parameters) together with an SpO2 (lower bandwidth parameter) signal.
Although the solutions as discussed above already provide a significant improvement over single-parameter telemetry systems, it is still an object of the present invention to reduce the amount of required monitoring logistics and to further improve the patient""s comfort, freedom and privacy by decreasing the number and volume of devices directly or indirectly attached to the patient.
The invention solves this object by providing transmitters, according to the independent claims, in wireless telemetry systems, preferably for medical purposes, thus providing open multi-parameter telemetry systems. Preferred embodiments are shown by the dependent claims.
As a first aspect, a transmitter physically comprises a (local) sensor, normally located within a transmitter casing, for sensing a first parameter, a data transmission unit for providing a wireless transmission to a receiver of the telemetry system, and a coupling unit for coupling one or more remote sensors to the transmitter. While the transmitter is designed to transmit signals from the local sensor, it also allows to further or alternatively transmit signals from one or more remote sensors coupled to the coupling unit. This allows changing monitoring from one parameter to another parameter by simply coupling another remote sensor to the coupling unit. Accordingly, a further parameter might be monitored (within the constraints of limited transmission bandwidth) by coupling a further remote sensor to the coupling unit. Thus, for changing the parameter(s) to monitor, the transmitter already applied to the patient needs not to be changed or removed from the patient. Simply, another remote sensor is coupled to the coupling unit.
In a preferred embodiment, the transmitter further comprises a selecting unit for selecting data supplied from the local and/or the remote sensor(s) to be transmitted by the transmitter. The selecting unit allows to manually and/or automatically select the data to be transmitted, e.g. in accordance with bandwidth or other transmission path constraints. Possible criteria for selecting data to be transmitted can be physiological data (e.g. xe2x80x9cselect the physiologically most meaningful sensor, when more than one sensor provide data about the same parameter(s)xe2x80x9d), mechanical information (e.g. by a plugged sensor detection), electrical information (e.g. electrode impedance detection), alarm condition(s) (e.g. xe2x80x9ctransmit parameter A after a certain alarm has occurredxe2x80x9d), and/or status condition(s) (e.g. xe2x80x9ctransmit parameter A only when a certain condition of the patient has been detectedxe2x80x9d).
As a second aspect, a transmitter comprises a data transmission unit for providing a wireless transmission to a receiver of the telemetry system, and a coupling unit for coupling one or more sensors to the transmitter. The coupling unit provides an interface allowing any sensor to couple to the transmitter via a predefined protocol.
Thus, the invention provides the following advantages:
Optimum use of limited Radio Frequency spectrum by transmitting multiple parameters within one single RF channel.
Easy logistics. The hospital needs only a few different transmitters (or wireless transducers), each having multiple parameter capability.
Selection of optimum parameter is possible at patient side without changing transducers.
It is clear that the invention can be partly or entirely embodied by one or more suitable software programs, which can be stored on or otherwise provided by any kind of data carrier, and which might be executed in or by any suitable data processing unit.